1. Field of the Invention
The present invention relates to a method, a machine and a mold for fabricating, by injection of synthetic material, containers having a film forming an external at least partial coating and forming an integral part of the containers, and the containers thus obtained.
2. Description of the Prior Art
When it is desired, in particular, to decorate such containers obtained by injection of synthetic material, or to apply thereto indications relating more particularly to the composition of the product contained, a current technique includes printing the decoration and the indications directly on the container already produced. This technique has numerous drawbacks because more particularly of the poor quality of printing on the material, generally polypropylene or similar, of the container, and because of the need for an additional operation for doing this, which operation increases the costs and the manufacturing time.
To overcome these drawbacks, synthetic material is injected on a printed film, cut out previously to the desired format, which is placed in the mold before injection. In this case, very good printing qualities can be obtained and the pellicule is incorporated in the container at the same time as this latter is manufactured, without loss of time and without additional cost.
Thus, French Pat. No. 2 210 504, particularly, discloses a method of incorporating a thin film of material in an object made from a thermoplastic material; the object being made by means of an injection machine including more particularly a mold formed of a male punch element and a female die element, and at least one synthetic material injection nozzle. More particularly, the method includes the following steps:
feeding the mold with films previously cut out to the desired format,
holding the film applied against the male element during closure of the mold; and
injecting synthetic material in the space left between the male and female elements when said mold is closed.
Referring to the accompanying FIG. 1 illustrating this prior art, the mold 1 used for implementing this method comprises a punch 2 and a die 3. The synthetic material injection nozzle 4 is provided in the die 3 and opens into the central zone at the bottom of the cavity of the die; said zone being formed as an arcuate part 5 projecting outwardly. This arcuate part 5 is arranged so as to be housed in the corresponding concave recess 6 in the punch 2. This latter has slits or openings 7, connected to a suction system not shown, for holding the film 8 against the punch during closure of the mold. Thus, in this case, when the film must be on the outside of the container, this latter, as illustrated in FIG. 1, must have a central hole through which the synthetic material is injected.
The synthetic material thus injected between the punch and the film applies this latter against the walls of the die, while forming a container of which the film, forming for example a label or a decoration, forms an integral part.
The essential disadvantage of this method resides as has been seen, in the need to form a recess in the film for passing the injected material therethrough. That requires an additional step in forming the film, whence a loss of time and increase in cost. The advantage of using a preinjected film is therefore largely reduced for this reason. Furthermore, such a hole is unesthetic and makes the use of the film as label impractical. In fact, the indications concerning for example the composition of the product, which are generally printed on the part of the film covering the bottom of the container, are interrupted by this hole.
The purpose of the present invention is precisely to overcome this drawback by proposing a method, a machine and a mold for fabricating containers, made from an injected material, including an external coating film forming an integral part of the container, without it being necessary to form a central hole in said film.